The invention relates to a screen wiper arrangement comprising a window screen and a screen wiper for cleaning the window screen and a method for operating the screen wiper arrangement.
It is known in the art that cabins of e.g. mobile or stationary construction equipment and working machines have a window screen with a screen portion which can be moved with respect to a fixed screen portion. When the movable screen portion is in its open position, the screen wiper would be damaged when started or operated in such a case.
JP 6156069 discloses a device which detects if the front window of an excavator is closed or open. A sensor is arranged in an actuator device located in a movable arrangement provided for opening or closing the window screen. When the window screen is open it is impossible to start the wiper.
GB 353366 A discloses a screen wiper arrangement comprising a window screen and a screen wiper for cleaning the window screen which is arranged in an opening of a cabin and inserted in a window frame. The window screen can be moved between an open and a closed position. A wiper motor is arranged at the window screen An electrically conductive element in form of a contact pin is arranged at the casing of the wiper motor which opens or closes an electrical circuit between a battery and the wiper motor depending on the position of the window screen. The contact pin makes mechanical and electrical contact to a spring element in order to establish an electrical connection between the vehicle battery and the wiper motor when the window screen is closed.
It is desirable to provide a screen wiper arrangement which prevents the action of a screen wiper independent of an actuator device for moving a movable window screen.
It is also desirable to provide a method for operating such a screen wiper arrangement.
A screen wiper arrangement is proposed comprising a window screen and a screen wiper system for cleaning the window screen, wherein the window screen is arranged in an opening of a cabin and inserted in a window frame, and wherein the window screen comprises at least one screen portion which can be moved between an open and a closed position. The window screen comprises an electrically conductive element coupleable to an electrical circuit which has at least a first state in response to a first position of the at least one screen portion and a second state in response to a second position of the at least one screen portion. One or more contact points are available for detecting if the electrical circuit is in the first or the second state, and a wiper control element is provided which controls the activation of the screen wiper system depending on the actual state of the electrical circuit.
The electrically conductive element is electrically coupleable to a first contact point and a second contact point arranged in operational connection with the at least one screen portion. The electrically conductive element can be embodied as a simple wire attached to, or a conductive thin film deposited onto, the at least one screen portion. The two contact points can be electrically connected to each other by the electrical conductive element when the screen portion comprising the electrically conductive element is placed on the appropriate location.
In a favourable embodiment according to the invention, the electrically conductive element can be an inductor. The position of the at least one screen portion can be detected without physical contact between the one or more contact points and the electrically conductive element.
A major achievement of the invention is that the actual position of the at least one screen portion is reliably detectable and that an activation of the screen wiper system is automatically prevented in case it is detected that the at least one screen portion is in a position wherein the screen wiper could be damaged if operated.
The screen wiper system comprises usually a screen wiper and an integrated washer. In cases where the screen wiper and the washer shall not be operated when said at least one screen portion is (partly or completely) open, according to the invention a screen wiper movement and/or emission of water from the washer integrated in the screen wiper system is triggered accordingly so that no water is emitted and the screen wiper does not move when the at least one screen portion is in an open position.
Advantageously, the at least one screen portion can be moved manually or by way of an actuator. A separate voluminous equipment for detecting whether the at least one screen portion is in its closed position can be avoided. The one or more contact points used according to the invention can be kept small and can be arranged at unobtrusive positions, for instance integrated in a window frame or a guide for the at least one screen portion.
The electrically conductive element used according to the invention can be easily detected by a counterpart being responsive to the actual position of the at least one screen portion. The electrically conductive element can be a wire, a thin-film layer, an electric component, particularly an inductor, and the like. The counterpart can be a contact pad which engages the electrically conductive element when the at least one screen portion is in an appropriate position. The counterpart can be a detector which detects the presence and/or absence of the at least one screen portion at an appropriate position.
In a favourable embodiment according to the invention, any temporary intermediate positions of the at least one screen portion between the first and second position which the at least one screen portion will pass during its movement between the first and second position, and/or any permanent intermediate position between said first and second position, can be assigned to one of the two states of the electrical circuit. By identifying intermediate positions of the at least one screen portion it can be easily detected if the at least one screen portion is started to be opened, thus allowing a reliable inhibition of the operation of the screen wiper system or even an interruption of an ongoing screen wiper system operation. This is particularly useful in case that the opening and closing of the at least one screen portion is not done manually but (unintentionally) by electrical actuation.
In a favourable embodiment according to the invention, the one or more contact points can be arranged at a first frame portion corresponding to the at least one screen portion in its closed state. In this case, the contact points interact with the at least one screen portion when the at least one screen portion is in its closed position.
Additionally or alternatively, the one or more contact points can be arranged at a second predefined location, for instance a frame portion or another stowing-away position of the at least one screen portion, corresponding to the open state of the at least one screen portion. The stowing-away position can be at a predefined location of the chassis, for instance at the door and the like. In this case, the contact points interact with the at least one screen portion when the at least one screen portion is in its open position.
Generally, there can be a combination of contact points at the first frame portion and the second location. In all three cases, the electric circuit can change its state, for instance being open, closed or changing its electrical resistance. The electrical circuit can also be employed for other purposes in the cabin, and the position of the one or more contact points can be adapted to the requirements of the electric circuit.
In a favourable embodiment according to the invention, the electrically conductive element can be an electrically conductive wire. An electric wire can be easily attached to the at least one screen portion.
In a favourable embodiment according to the invention, the electrically conductive element can be electrically coupleable to a first contact point and a second contact point arranged in operational connection with the at least one screen portion. The electrically conductive element can be embodied as a simple wire attached to, or a conductive thin film deposited onto, the at least one screen portion. The two contact points can be electrically connected to each other by the electrical conductive element when the screen portion comprising the electrically conductive element is placed on the appropriate location.
In a favourable embodiment according to the invention, the electrically conductive element can be integrated in an electric window heater arranged at the window screen. Particularly, the electrically conductive element can be a conductive path integrated in an electric window heater arranged at the at least one screen portion. The detection whether the window screen is closed or open can comfortably be integrated in an electric equipment which is already integrated in the window screen.
In a favourable embodiment according to the invention, a voltage drop measured between a first and a second contact point can have a lower value when the at least one screen portion is in its closed position and can have a higher value when the at least one screen portion is in its open position or started to be opened.
Particularly, the electric circuit can be closed by the electrically conductive element of the at least one screen portion when the at least one screen portion is in its closed position and open when the when the at least one screen portion is in its open position or started to be opened. When the at least one screen portion is in its closed position, the electrically conductive element can form an electric connection between the two contact points. The position of the at least one screen portion changes the electrical properties, e.g. the electrical resistance or another state of the electric circuit, in a well defined way which can easily monitored.
Alternatively, in a favourable embodiment according to the invention, a voltage drop measured between a first and a second contact point can have a higher value when the at least one screen portion is in its closed position and can have a lower value when the at least one screen portion is in its open position or started to be opened. Particularly, the electric circuit can be open when the at least one screen portion is in its closed position and closed when the at least one screen portion is in its open position. As already mentioned before, the change of the electrical properties of the electric circuit according to the actual position of the at least one screen portion can be easily detected.
In a favourable embodiment according to the invention, the electric circuit can comprise a radio frequency receiver responsive to the inductor. Favourably, the electrically conductive element can be embodied as an RFID tag (Radio
Frequency Identification tag). As it is known from the prior art RFID tags can be brought into wireless operational contact with corresponding high frequency transmitter, receiver or transceiver systems which are adapted or adaptable to the RFID tag used (or vice versa using RFID tags which are adapted or adaptable to the system used). The electric circuit can easily detect the presence or absence of the inductor or the RFID tag.
According to another aspect of the invention, a method is proposed for operating a screen wiper arrangement for a window screen according to anyone of the above described features, wherein an activation of a screen wiper is blocked or allowed depending on an actual state of an electric circuit coupled to an electrical conductive element arranged at the window screen. Favourably, the screen wiper system can be protected in a reliable and comfortable way against damage when the movable screen portion is open or started to be opened.
The invention is particularly useful for mobile or stationary work machines or construction equipment with cabins such as wheel loaders, haulers, excavators, dumpers, pipe layers, etc.